Sweet and Sour Spot

General Discussion
1

Ladies and Gentlemen,

 

i am a longtime reader of this forum and have posted a few times. This forum has been the most important source of information that helped me to shape a dozen surf boards in a garage and i am stoked. thank you for that, honestly, the info and individual help on this forum is invaluable! I’d need advice for one of my latest creations, a quad fish, 6’0" x  20 3/4  x 2 5/8, slight single to double concave, epoxy over EPS foam. It is a purple pigment tint that turned pink (not enough pigment), voila:

 

flat rockered

 

i have made plywood quad fins for that board:

back fins:

fin size: 4" high, chord length 3 1/2"

position: trailing edge 6 5/16" (16cm) from tail and 3 5/16" (8,5cm) off the rail

 

front fins:

fin size: 4 1/2" high, chord length 4 1/2"

position: trailing edge 11 1/2" from tail, 1 1/4" off rail

 

I don’t mind the colour, I am writing because it does surf great, BUT ONLY if my stance after the take off is EXACTLY right. I’ve taken off on waves, leaned into the bottom turn and the board just went straight. I remember waves on which i wildly kept repositioning my back foot… I especially remember a huge wave on my last surftrip to Morocco where that happened - for me it was one of the biggest days I was ever out, a massive swell, 17sec period, after endless paddling in strong currents I finally manage to position myself right in the lineup, I get a set wave, wow, this is big, just go, endless drop down a massive face, slightly choppy, damn, this is not going to work, the board is swerving from side to side, I try to correct backfoot, damn, doesn’t work, I am leaning into the bottom turn, aaaaaahhhhhh… wipeout!

whenever my backfoot is a bit off it doesn’t want to turn or it feels like i have to force the board to turn …whenever the backfoot is right ( right on top of the fin cluster), the board works just fine - fishy, fast, drivey…

You call that SWEET SPOT, right?  It’s TOO SMALL!

Q: how can I make it BIGGER?  

Answer: “work on your take off and bottom turn”

… you are probably right… I am just an average surfer, unfortunately not getting more than 4 weeks of surf each year ( I am 33 years old and live 10 hours away from the next break)… so surfing tipps are also welcome, really!

BUT… this is a design forum… and I hope some change in design will help me widen the sweet spot of this board…  maybe fin position or fin type/ shape? 

…and I have built another board for a friend, slightly pulled in tail and nose compared to the pink board, with a thruster fin set up, which does not show these problems AT ALL! no matter how I land on it after taking off, it seems to do what it is supposed to do!!! the problem is, my friend will not give it back to me (This is me in the pic, I should have kept it!)

 

widepoint more in center, more curve in outline, a bit less volume…

now, maybe I am comparing apples and oranges here, but is there a way to make the pink board as predictable as the thruster, to cure the symptoms described above?

 

any help greatly appreciated… 

 

cheers!

 

http://lungfish.twoday.net/

 

 

 

2

My guess is your fin placement. Post a shot straight of the fins from above.

3

Hi candor,

 

here’s the shot:

 

 

 

what do you think?

 

4

Hi Karl

I think the rear fins may be too far off the rail, making it difficult to initiate a turn???

5

Quads are notoriously sensitive to fin sizes, placement, toe-in and cant.  As a template, fishes are a somewhat extreme design that have less rail line, less curve in the tail, and require more technique in order to trim and turn. Putting the two design elements together results in a combo that’s easier than average to mess up.

To my eye the rear fins look like they have too much cant relative to their placement, and the inboard placement is kind of working against the wide tail.  If it were my board I’d move the rear fins to the rail, use the same toe-in as the fronts but with a little less cant.  Then I’d plan on surfing the board like a fish and not try to emulate the same style I use when surfing a thruster.  

6

Gdaddy has it worked out for you.

I shaped a buddy a board almost identical to yours and we went with 1 1/4" off the rail for front and back and also he uses 4* inserts on the front and 2* inserts in the back. We towed the front 3/16" adn the rear 1/8". He claims that it surfs fairly well top to bottom but it is NOT a thruster. It is a quad set up on a traditional fish outline and rocker and it surfs, as you would expect, alot like a keel fish.

Surf it like it is intended and you will enjoy it more. Keep your center of gravity low. Go with the flow.

Terry

7

 

gdaddy, 

 

thank you for your reply. do you think fin size is appropriate? I have re-sized the back fins once, cutting 1/4 inch off their bases as the board felt a bit stiff and then glassed them on again. this helped a bit but maybe was not enough?

for the fin position i used the mckee formula by the way, but maybe that's better suited for narrower tails? 

you wrote "Then I'd plan on surfing the board like a fish and not try to emulate the same style I use when surfing a thruster." Maybe you could explain that a bit more?

8

cool! thank you heaps for the numbers… so… I actually DO mean to surf like it is intended. and in my DREAMS I CAN :slight_smile: know what I mean? maybe with a new fin placement it will work better…

you know, I don’t really want a thruster per se… this thruster for my friend was actually the first thruster I have ever shaped (I have shaped keel fish and quads before that worked fairly well… pink quad worked the best so far…) and I told him that I don’t know if it will work… and then it worked just really well for him and as soon as I tried i knew it’s a great board… it’s board number 12, and it is an exciting journey. I feel that our surfing (I only build for me and a handfull of friends) improved with those boards and that’s just a fantastic thing…

so traditional fish surfing means lower center of gravity?

excuse me for asking naive questions here, might be due to lack of ocean and surf nearby…

 

 

9

karl! thanks for your reply… seems that everybody agrees with you…

 

10

There seem to be a lot of different ways to set up a quad cluster.   My understanding of them is a lot more limited than that of other posters in this forum so maybe I should just shut up and wait for one of them to provide you with a more informed perspective for your particular situation.  I merely commented on what I would do if I was in your situation.    

 

My understanding of the McKee formula is that it results in a fin cluster that rides more similarly to that of a thruster rather than a twin.  The rail-based fin clusters ride more similarly to a twin than a thruster.  The fish design itself started off as the epitome of a twin, which brings us back to the different surfing style that compliments the fish design.  If you watch the surfers who are really good at surfing a fish you’ll notice most of them don’t pump those boards the way the performance shortboard guys move.  Fish riders generally favor that compress-and-release motion as they pump up and down the face.   They crouch down low and push off on their bottom turns.  Most of them aren’t doing a lot of butt wiggling and double pumping on the face to build speed prior to their turns - they don’t need to because the straight outilines and flat rockers of a fish coupled with the drive of those keels generates its own speed.  Adding the quad to the mix results in more stability and control due to breaking up all that fin area on the rail, albeit at the expense of a little loss of drive.   They’re a bit more of a compromise but result in a little more versatility over a wider range of conditions.  

 

Some people say that it’s harder to surf a fish well, others say it’s easier.  Lot’s of people have commented that surfing a fish too much ruins your shortboard style.  I think most people who surf both would agree that they require a different approach.  

 

 

11

Once again Gdaddy has it nailed. I am anything but an expert. I have only built one quad fish and the only reason that I even commented was to give you some of the numbers that I used and seemed to get lucky with. Your board is similar enough that they might also work for you.   WARNING!!!!   I AM NOT AN EXPERT!!!! I AM A GARAGE HACK!!!

I see alot of guys that surf fishes well have the low stance and smooth top to bottom rythmic style that Gdaddy was refering to. I think that if you push a fish too far onto the rail without a low center of gravity you will have the results that you are having. Stay low initiate your turn and be patient and wait for the board to turn. You cant whip them around like you would a thruster or modern performance board.

My .02 worth.

Terry

12

I like to use the mckee setup for quads also,except I place front and rear fins 1 1/4" from the rail and toe them in the same 1/8"-1/4".I also give the fins the same kant front and back,usually 4-6 degrees.This has worked for me on several boards and is worth a try if you haven’t tried it.